Manifold electrification process

ABSTRACT

A process for improving the imaging characteristics of electrically photosensitive material employed in the manifold layer transfer imaging process which comprises subjecting the material to an electric field of known polarity and then reversing the polarity of the field prior to the exposure of the imaging material to electromagnetic radiation to which it is sensitive.

United States Patent 11 1 Krohn et al.

[ Feb. 27, 1973 MANIFOLD ELECTRIFICATION PROCESS [75] Inventors: Ivar T.Krohn; Geoffrey A. Page,

' both of Rochester, N.Y.

[73] Assignee: Xerox Corporation, Rochester, N.Y.

[22] Filed: June 3, 1969 [211 App]. No.: 829,963

52 us. 01. ..'...96/1.3, 96/1 R, 96/15 [51] Int. Cl. ..G03g 13/22 [58]Field of Search ..96/1, 1.3, 1.5

[56] References Cited UNITED STATES PATENTS 3,041,167 6/1962 Blakney eta1. .Q ..96I1.4 X 3,355,289 11/1967 Hall et a1. ..96/l.4 3,412,24211/1968 Giaimo 1.96/1 X 2,833,648 5/1958 Walkup ..96/1

3,268,331 Harper ..96/1 3,438,772 4/1969 Grundlach ..96/1 3,446,6165/1969 Clark ..96/1.5 3,457,070 7/1969 Watanabe et al.... ..96/1.43,512,968 5/1970 Tulagin ..96/1.2

Primary Examiner-George F. Lesmes Assistant Examiner-John R. MillerAttorney-James J. Ralabate, David C. Petre and Raymond C. Loyer [5 7]ABSTRACT A process for improving the imaging characteristics ofelectrically photosensitive material employed in the manifold layertransfer imaging process which comprises subjecting the material to anelectric field of known polarity and then reversing the polarity of thefield prior to the exposure of the imaging material to electromagneticradiation to which it is sensitive.

12 Claims, 2 Drawing Figures PATENTED Z' 7 INVENTORS lVAR T4 KROHNGEOFFREY A. PAGE @m za%w ATTORNEY MANIFOLD ELECTRIFICATION PROCESSBACKGROUND OF THE INVENTION The present invention relates to manifoldlayer transfer imaging and more specifically to a process which providesimproved imaging characteristics of the electrically photosensitivematerials employed therein.

Although color imaging techniques based on the transfer of an imaginglayer have been known in the past, these techniques have always beendifficult to operate because they depend on photochemical reactions andgenerally involve the use of distinct layer materials for the twofunctions of imagewise transfer and image coloration. A typical exampleof the complex structures and sensitive materials employed in prior arttechniques is described in US. Pat. No. 3,09l,529 to Buskes. A morecomprehensive discussion of prior art imaging techniques based on layertransfer may be found in copending application Ser. No. 452,641, filedMay 3, 1965, in the U.S. Patent Office, now abandoned.

Copending application Ser. No. 452,641, filed May 3, 1965 now abandoned,describes an imaging system utilizing a manifold sandwich comprising anelectrically photosensitive material between a pair of sheets. In thisimaging system, an imaging layer is prepared by coating a layer ofcohesively weak electrically photosensitive imaging material onto asubstrate. In one form the imaging layer comprises an electricallyphotosensitive material such as metal-free phthalocyanine dispersed in acohesively weak insulating binder. This coated substrate is called thedonor. When needed, in preparation for the imaging operation, theimaging layer is activated as by contacting it with a swelling agent,solvent, or partial solvent for the material, or by heating. This stepmay be eliminated, of course, if the layer retains sufficient residualsolvent after having been coated on the substrate from a solution orpaste or if sufficiently cohesively weak to fracture in response to theapplication of electromagnetic radiation and electrical field. Afteractivation a receiving sheet is laid over the surface of the imaginglayer. An electric field is then applied across the imaging layer whileit is exposed to a pattern of light and shadow representative of theimage to be reproduced. Upon separation of the donor substrate or sheetand receiving sheet, the imaging layer fractures along the lines definedby the pattern of light and shadow to which the imaging layer has beenexposed. Part of the imaging layer is transferred to one of the sheetswhile the remainder is retained on the other sheet so that a positiveimage, that is, a duplicate of the original is produced on one sheetwhile a negative image is produced on the other.

Copending application Ser. No. 609,058, filed Jan. 13, I967, nowabandoned, described a, modified manifold imaging process wherein theelectric field across the imaging layer is modified by reducing,grounding or reversing the field after image exposure of the imaginglayer. By such means the image sense normally obtained in the manifoldimaging process is reversed. That is, the respective sheets upon whichthe positive and negative image are obtained are reversed when theelectric field employed during the imaging step is modified subsequentto the imaging step but prior to sandwich separation.

In the manifold imaging process the imaging layer containing theelectrically photosensitive materials can be exposed in severaldifferent modes. That is, conventionally a transparent donor sheet isemployed and the imaging layer is exposed through the donor sheet. Insome instances it is preferred that the imaging layer be exposed fromthe receiver side of the manifold sandwich through a transparentreceiver. Also the imaging layer can be exposed prior to beingincorporated into a manifold sandwich by electrically charging a donorsheet and imaging layer, then exposing it to an imagewise pattern oflight and shadow either through a transparent donor sheet or directly onthe uncovered surface of the imaging layer.

Although usable images are obtained by the various imaging modes andimage sense reversal procedures, a great variety of image quality isobserved between different electrically photosensitive materials. Thatis, some materials provide reduced image quality when subjected to fieldreversal after imaging while other materials may provide inferior imagequality or require large amounts of light when exposed from the receiverside of the manifold sandwich. A process has been discovered whichimproves the quality of images ob tained from such imaging materialswhen exposed from the receiver side of the manifold sandwich orsubjected to field reversal after imagewise exposure.

SUMMARY OF THE INVENTION An object of this invention is to provide alayer transfer imaging process wherein images of improved quality areobtained.

Another object of this invention is to provide a manifold layer transferimaging process wherein high quality images are obtained when theimaging layer is exposed through the receiver side of the manifoldsandwich.

Another object of this invention is to provide a manifold imagingprocess wherein images of improved quality are obtained with image sensereversal techniques.

Another object of this invention is to provide a process for improvingthe imaging characteristics of electrically photosensitive materialemployed in the manifold imaging process.

In accordance with this invention, electrically photosensitive imagingmaterials are subjected to an electrification treatment which comprisessubjecting the material to an electrical field of known polarity whilein the dark and subsequently reversing the electrical field while stillin the dark. After field reversal the imaging material may be imageexposed from the receiver side of the manifold sandwich to produceimproved quality images. In addition, the imaging material providesimproved quality images of reversed image sense when subjected to suchtechniques as field modification as described in copending applicationSer. No. 609,058 referred toabove and excess exposure to electromagneticradiation as described in copending application Ser. No. 609,124 filedJan. 13, 1967, now abandoned, both applications being incorporatedherein by reference.

Previously, some of the electrically photosensitive materials useful inthe manifold imaging process provided high quality images in the variousimaging modes and image reversal techniques whereas other electricallyphotosensitive materials provided images of varying quality dependentupon the imaging mode employed in the manifold imaging process. Inaccordance with the process of this invention, the electricallyphotosensitive materials useful in the manifold imaging process arerendered versatile in that high quality images are produced even whenexposed to imagewise light from the receiver side of imaging layer andwhen image sense reversal techniques are employed.

The electrification treatment of this invention involves subjecting amaterial to an electric field. The electric field is provided by meansknown to the art to subject an area to an electric field. Thus, theelectrically photosensitive material can be incorporated into a manifoldsandwich and subjected in the dark to an electric field by placing thesandwich between a pair of electrodes. The polarity of the electricfield between the electrodes is then reversed and, providing thereceiver side electrode receiver sheets are transparent, theelectrically photosensitive material can then be exposed to a pattern ofelectromagnetic radiation to which it is sensitive. Preferably thereceiver is removed with the field still applied and a fresh receiverplaced over the imaging layer prior to reversing the polarity of thefield. The electric field can also be provided by employing anelectrically insulating material in at least one of the sheets formingthe manifold sandwich and producing a static charge in the insulatingsheet. By employing the insulating sheets, which retain an electriccharge, the manifold sandwich can be passed between and in contact withcharge bearing members such as electrically charged rollers whereby anelectric charge is transferred to the static sheets. Field reversal isaccomplished by passing the manifold sandwich through two such chargebearing members prior to exposing the electrically photosensitiveimaging material to a pattern of electromagnetic radiation. Thus, thestatic charge is developed by providing an electrical charge bearingmember in electrical communication with the electrically insulatinglayer.

The electric field employed in the process of this invention isdesirably in the range of from 2,000 to 10,000 volts per mil across theimaging layer. Preferably the electric field is in the range of fromabout 3,000 to 7,000 volts per mi]. The reversed field is usually of thesame strength as the initial electric field. To attain such electricfield with static charges in insulating layers, a potential of fromabout 5,000 to about 20,000 volts in the charge bearing member isusually employed. Higher voltages can be employed but are not desirable.

In one form, the process of this invention can be accomplished bypassing a donor, that is, a substrate having coated thereon anelectrically photosensitive imaging material, between a pair of rollerelectrodes or into the ionization area of corona discharge device andthen incorporating the donor into a manifold sandwich and subjecting theimaging layer to a reversed electrical field. The static chargesretained in insulating donor and receiver sheets are sufficient toprovide an electric field across the sandwich during subsequent imageexposure and sandwich separation steps in the manifold imaging process.

When combined with the manifold imaging process, the means employed toprovide the electrical field for the treatment process of this inventioncan also be employed to provide the electric field in the manifoldimaging process. The electrodes employed may comprise any suitableconductive material and may be flexible or rigid. Typical conductivematerials include metals such as aluminum, brass, steel, copper, nickel,zinc, etc., metallic coatings on plastic substrates, rubber renderedconductive by the inclusion of a suitable material therein or paperrendered conductive by the inclusion of a suitable material therein orthrough conditioning in a humid atmosphere to insure the presencetherein of sufficient water content to render the material conductive.Such electrodes are, for example, conductive rollers or corona dischargedevices as described in U.S. Pat. No. 2,588,699 to Carlson and U.S. Pat.No. 2,777,957 to Walkup, U.S. Pat. No. 2,885,556 to Gundlach or by usingconductive rollers as described in U.S. Pat. No. 2,980,834 to Tregay etal. Other means of transmitting a static charge will occur to thoseskilled in the art.

In the manifold imaging process wherein the imaging layer is exposed toactivating electromagnetic radiation while positioned between theelectrodes which establish the electrical field across the sandwich, oneof the electrodes must be at least partially transparent. Thetransparent conductive electrode may be made with any suitableconductive transparent material and may be flexible or rigid. Typicalconductive transparent materials include: cellophane, conductivelycoated glass, such as tin or indium oxide coated glass, aluminum coatedglass, or similar coatings on plastic substrates. NESA, a tin oxidecoated glass, available from Pittsburgh Plate Glass Company is preferredbecause it is a good conductor, highly transparent and is readilyavailable. In the process of this invention wherein the donor and/orreceiver is composed of conductive material, each may also be used asthe electrode by which the imaging layer is subjected to an electricfield. That is, either one or both of the donor sheet and receiversheets may serve a dual function in the process of this invention.

The electrification treatment of electrically photosensitive materialsin accordance with this invention can be conveniently employed inconjunction with the manifold layer transfer imaging process. Theimaging process employes an electric field across the imaging layer atsome point in the process prior to the separation of the manifoldsandwich. Although the electrification treatment can be performed onelectrically photosensitive materials at some point in time and locationand remote from the manifold imaging process, the electrificationtreatment is conveniently performed in conjunction with the imagingprocess. Thus, a donor sheet having an imaging layer coated thereon can,immediately after the reversed potential is applied be imagewise exposedto electromagnetic radiation to which. it is sensitive and furtherprocessed in accordance with the manifold imaging process to providenegative and positive copies of the original image.

The process of this invention can be employed to improve any suitableelectrically photosensitive material. Typical organic electricallyphotosensitive materials include: quinacridones such as 2,9-dimethylquinacridone, 4,11-dimethyl quinacridone, 2,10-dichloro-6,13-dihydro-quinacridone, 2,9-dimethoxy-6,13- dihydro quinacridone,2,4,9,1l-tetrachloro-quinacridone, and solid solutions of quinacridonesand other compositions as described in U.S. Pat. No. 3,160,510;carboxamides such as: N-2"-pyridyl-8,13- dioxodinaphtho-(2,1-2',3')-furan-6-carboxamide, N- 2"-(l",3",5"-triazyl-8,l3-dioxodinaphtho-(2,1-2

' ,3 )-furan-6-carboxamide, anthra-( 2,1 )-naphtho-( 2,3 d )-furan-9,14-dione-7-(2'-methyl-phenyl) carboxamide; carboxanilides such as:8,13-dioxodinaphtho- (2,1-2',3 ')-furan-6-carbox-p-methoxy-ani1ide,8,13- dioxodinaphtho-( 2, l -2 ,3 )-furan-6-carbox-pmethylanilide,8,13-dioxodinaphtho-(2,l-2',3 )furan- 6-carbox-p-cyanoanilide; triazinessuch as: 2,4- diamino-triazine, 2,4-di (1'-anthraquinonyl-amino)-6- l'-pyrenyl )-triazine, 2,4-di( l '-anthraquinonylamino)-6-(1"-naphthyl)-triazine, 2,4-di(l'-naphthylamino)-6-(l'-perylenyl)-triazine, 2,4,6-tri (l',1",1"'-pyrenyl) triazine, 2,4,6-tri (l,l",1"' -pyrenyl) triazine;benzopyrrocolines such as: 2,3-phthaloyl-7,8- benzo-pyrrocoline,1-cyano-2,3-phtha1oyo-7,8- benzopyrrocoline, l-cyano-2,3-phtha1ocy-5-nitro-7 ,8- benzopyrrocoline, l-cyano-2,3-phthaloyl-5-acetamido-7,8-benzopyrrocoline; anthraquinones such as: 1,5-bis-(beta-phenylethylamino) anthraquinone, l,5-bis-(3'- methoxypropylamino)anthraquinone, 1 ,5-bis (benzylamino) anthraquinone, 1,5-bis(phenylbutylamino) anthraquinone, 1,2,5,6-di(c,c-diphenyl)-triazole-anthraquinone, 4-(2'-hydroxyphenylmethoxyamino) anthraquinone;azo compounds such as: 2,4,6-tris(N-ethyl-N-hydroxyethyl-p-aminophenylazo) phloroglucinol, l ,3 ,5,7-tetra-hydroxy-2,4,6,8-tetra (N-methyl-N-hydroxyethyl-p-amino-phenylazo) naphthalene, 1,3,5-trihydroxy-2,4,6-tri (3 '-nitro-N-methyl-N-hydroxymethyl-4'-aminophenylazo) benzene,3-methyl-1-phenyl-4-(3' pyrenylazo)-2- pyrazolin-S -one, 1-( 3'-pyrenylazo )-2-hydroxy-3- naphthanilide, 1-( 3-pyrenylazo)-2-naphthol, l-( 3 pyrenylazo )-2-hydroxypyrene, l-( 3 'pyreny1azo)-2-hydroxy-3-methyl-xanthene, 2,4,6-tris (3'-pyrenylazo) phloroglucinol,2,4,6-tris (l-phen-anthrenylazo) phloroglucinol, l-(2-methoxy-5'-nitro-phenylazo)-2- hydroxy-3'nitro-3-naphthanilide; salts and lakesof compounds derived from 9-phenylxanthene, such as:phosphotongstomolybdic lake of 3,6-bis (ethylaminoy 9,2'-carboxyphenylxanthenonium chloride, barium salt of 3-2-toluidineamino-6-2"-methy1-4"-sulphophenyl-amino-9-2 '-carboxyphenylxanthene; phosphomolybdic lake of3,6-bis (ethylamino)-2,7- dimethyl-9,2'-carbethoxy-phenylxanthenoniumchloride; dioxazines such as: 2,9-dibenzoyl-6,l3-dichloro-triphenodioxazine, 2,9-diacetyl6,13-dichloro-triphenodioxazine, 3 ,10-dibenzoylamino-2 ,9- diisopropoxy-6 l3-dichlorotriphenodioxazine, 2,9-difuroyl-6,13-dichlorotripheno-dioxazine; lakes of fluorescein dyes,such as: lead lake of 2,7-dinitro-4,5- dibromo fluorescein, lead lake of2,4,5,7-tetrabromo fluorescein, aluminum lake of 2,4,5,7-tetrabromo-10,ll,l2,13-tetrachloro fluorescein; bisazo compositions such as:N,N-di[l-(l'-naphthy1azo)-2-hydroxy- B-naphthyl] adipdiamide,N,N'-di-l-(1 -naphthylazo 2-hydroxy-8-naphthyl succindiamide,bis-4,4'-(2"- hydroxy-B"N,N-diterephthala-mide-l-naphthylazo) biphenyl,3,3'-methoxy-4,4'-diphenyl-bis (1"-azo-2"- hydroxy-3"-naphth-anilide);pyrenes such as: 1,3,6,8- tetra-cyanopyrene,l,3-dicyano-6,8-dibromo-pyrene, 1 ,3 ,6,8-tetraaminopyrene,1-cyano-6-nitropyrene; phthalocyanines such as: beta-form metal freephthalocyanine, copper phthalocyanine, tetrachloro phthalocyanine, the xform of metal-free phthalocyanine as described in U.S. Pat. No.3,357,989; metal salts and lakes of azo dyes, such as: calcium lake of6-bromo-1 (1 '-sulfo-2-naphthylazo)-2-naphthol, barium salt of 6-cyano-1( l '-sulfo-2-naphthylazo )-2-naphthol, calcium lake of1-(2'-azonaphthalene-l'-sulfonic acid)-2- naphthol, calcium lake of 1-(4-ethyl-5 chloroazobenzene-Z'-sulfonic acid)-2-hydroxy-3- naphthoic acid;and mixtures thereof.

Typical inorganic electrically photosensitive materials include cadmiumsulfide, cadmium sulfoselenide, zinc oxide, zinc sulfide, sulphurselenium, mercuric sulfide, lead oxide, lead sulfide, cadmium selenide,titanium dioxide, indium trioxide and the like.

In addition to the aforementioned organic materials, other organicmaterials which may be employed in the imaging layer includepolyvinylcarbazole; 2,4-bis (4,4'- diethyl-amino-phenyl)-1 ,3,4-oxidiazole; N-isopropylcarbazole and the like. Other electricallyphotosensitive materials useful in the process of this invention arelisted in copending application Ser. No. 708,380, filed Feb. 26, 1968which is incorporated herein by reference.

It is also to be understood that the electrically photosensitiveparticles themselves may consist of any suitable one or more of theaforementioned electrically photosensitive materials, either organic orinorganic, dispersed in, in solid solution in, or copolymerized with,any suitable insulating resin whether or not the resin itself isphotosensitive. This particular type of particle may be particularlydesirable to facilitate dispersion of the particle, to preventundesirable reactions between the binder and the photosensitive materialor between the photosensitive and the activator and for similarpurposes. Typical resins of this type include polyethylene,polypropylene, polyamides, polymethacrylates, polyacrylates, polyvinylchlorides, polyvinyl acetates, polystyrene, polysiloxanes,

chlorinates rubbers, polyacrylonitrile, epoxies, phenolics, hydrocarbonresins and other natural resins such as resin derivatives as well asmixtures and copolymers thereof.

The x form phthalocyanine is preferred because of its excellentphotosensitivity although any suitable phthalocyanine may be used toprepare the imaging layer of this invention. The phthalocyanine used maybe in any suitable crystal form. It may be substituted or unsubstitutedboth in the ring and straight chain portions. Reference is made to abook entitled Phthalocyanine Compounds by F. H. Moser and A. L. Thomaspublished by the Reinhold Publishing Company, 1963 edition for adetailed description of phthalocyanines and their synthesis. As abovenoted, any suitable phthalocyanine may be used to prepare thephotoconductive layer of the present invention. Typical phthalocyaninesare listed in copending application Ser. No. 708,380 referred to above.

The basic physical property desired in the imaging layer of the manifoldimaging process is that it be frangible as prepared or after having beensuitably activated. That is, the layer must be sufficiently weakstructurally so that the application of electrical field combined withthe action of actinic radiation on the electrically photosensitivematerials will fracture the imaging layer upon separation of themanifold sandwich. Further, the layer must respond to the application offield, the strength of which is below that field strength which willcause electrical breakdown or arcing across the imaging layer. Anotherterm for cohesively weak, therefore, would be field fracturable.

Although the imaging layer must be cohesively weak in order to fracturein imagewise configuration in the manifold imaging process, theelectrically photosensitive material to be treated in accordance withthe electrification treatment of this invention need not be cohesivelyweak. The electrically photosensitive material to be treated may beincorporated into an imaging layer and treated in accordance with theprocess of this invention without rendering the layer cohesively weak.After treatment by the process of this invention, the layer may berendered cohesively weak by the application thereto of an activator aswill be more fully described below.

The imaging layer serves as the photoresponsive element of the system aswell as the colorant for the final image produced. Other colorants suchas dyes and pigments may be added to the imaging layer so as tointensify or modify the color of the final images produced when color isimportant. Preferably, the imaging layer is selected so as to have ahigh level of response while at the same time being intensely colored sothat a high contrast image can be formed by the high gamma system ofthis invention. The imaging layer may be homogeneous comprising, forexample, a solid solution of two or more pigments. The imaging layer mayalso be heterogeneous comprising, for example, pigment particlesdispersed in a binder.

One technique for achieving low cohesive strength in the imaging layeris to employ relatively weak, low molecular weight materials therein.Thus, for example, in a single component homogeneous imaging layer, amonomeric compound or a low molecular weight polymer complexed with aLewis acid to impart a high level of photoresponse to the layer may beemployed. Similarly, when a homogeneous layer utilizing two or morecomponents in solid solution is selected to make up the imaging layer,either one or both of the components of the solid solution may be a lowmolecular weight material so that the layer has the desired low level ofcohesive strength. This approach may also be taken in connection withthe heterogeneous imaging layer. Although the binder material in theheterogeneous system may in itself be photosensitive, it does notnecessarily have this property. Materials may be selected for use asthis binder material solely on the basis of physical properties withoutregard to their photosensitivity. This is also true of the two componenthomogeneous system where photoinsensitive materials with the desiredphysical properties can be used. Any other technique for achieving lowcohesive strength in the imaging layer may also be employed. Forexample, suitable blends of incompatible materials such as a blend of apolysiloxane resin with a polyacrylic ester resin may be used either asthe binder layer in a heterogeneous system or in conjunction with ahomogeneous system in which the photoresponsive material may be eitherone of the incompatible components (complexed with a Lewis acid) or aseparate and additional component of the layer. The thickness of theimaging layer whether homogeneous or heterogeneous ranges from about 0.2microns to about 10 microns generally about 0.5 microns to about 5microns and preferably about 2 microns.

The ratio of photosensitive pigment to binder by weight in theheterogeneous system may range from about 10 to l to about 1 to 10respectively, but it has generally been found that properties in therange of from about 1 to 4 to about 2 to 1 respectively produce the bestresults and, accordingly, this constitutes a preferred range.

The binder material in the heterogeneous imaging layer or the materialused in conjunction with the electrically photosensitive materials inthe homogeneous layer, where applicable, may comprise any suitablecohesively weak insulating material or materials which can be renderedcohesively weak. Typical materials include: microcrystalline waxes suchas: Sunoco 1290, Sunoco 5825, Sunoco 985, all available from Sun OilCo.; Paraflint RG, available from the Moore and Munger Company; paraffinwaxes such as: Sunoco 5512, Sunoco 3425, available from Sun Oil Co.;Sohio Paraowax available from Standard Oil of Ohio; waxes made fromhydrogenated oils such as: Capital City 1380 wax, available from CapitolCity Products, Co. Columbus, Ohio; Caster Wax L-2790, available fromBaker Caster Oil Co.; Vitikote L-304, available from Duro Commodities;polyethylenes such as: Eastman Epolene N-l l, Eastman Epolene C-l2,available from Eastman Chemical Products Co.; Polyethylene DYJT,Polyethylene DYLT, Polyethylene DYDT, all available from Union CarbideCorp.; Marlex TR 822, Marlex 1478, available from Phillips PetroleumCo.; Epolene C-l3, Epolene C-l0, available from Eastman ChemicalProducts, Co.; Polyethylene AC8, Polyethylene AC612, Polyethylene AC324,available from Allied Chemicals; modified styrenes such as: Piccotex 75,Piccotex 100, Piccotex 120, available from Pennsylvania IndustrialChemical; Vinylacetate-ethylene copolymers such as: Elvax Resin 210,Elvax Resin 310, Elvax Resin 420, available from E. l. duPont de Nemours81. Co., lnc., Vistanex Ml-l, Vistanex L-80, available from EnjayChemical Co.; vinyl chloride-vinyl acetate copolymers such as: VinyliteVYLF, available from Union Carbide Corp.; styrene-vinyl toluenecopolymers; polypropylenes; and mixtures thereof. The use of aninsulating binder is preferred because it allows for the use of a largerrange of electrically photosensitive pigments.

A mixtureof microcrystalline wax and polyethylene is preferred becauseit is cohesively weak and an insulator.

Where the imaging layer is not sufficiently cohesively weak to allowimagewise fracture, it is desirable to include an activation step in theprocess of this invention. The activation step may take many forms suchas heating the imaging layer thus reducing its cohesive strength orapplying a substance to the surface of the imaging layer or including asubstance in the imaging layer which substance lowers the cohesivestrength of the layer or aids in lowering the cohesive strength. Thesubstance so employed is termed an activator. Preferably, the activatorshould have a high resistivity so as to prevent electrical breakdown ofthe manifold sandwich. Accordingly, it will generally be found to bedesirable to purify commercial grades of activators so as to removeimpurities which might impart a higher level of conductivity. This maybe accomplished by running the fluids through a clay column or byemploying any other suitable purification technique. Generally speaking,the activator may consist of any suitable material having theaforementioned properties. For purposes of this specification and theappended claims, the term activator shall be understood to include notonly materials which are conventionally termed solvents but also thosewhich are partial solvents, swelling agents or softening agents for theimaging layer. The activator can be applied at any point in the processprior to separation of the manifold sandwich.

It is generally preferable that the activator have a relatively lowboiling point so that fixing of the resulting image can be accomplishedupon evaporation of the activator. If desired, fixing of the image canbe accomplished more quickly with mold heating at most. It is to beunderstood, however, that the invention is not limited to the use ofthese relatively volatile activators. In fact, very high boiling pointnon-volatile activators including silicone oils such asdimethyl-polysiloxanes and very high boiling point long chain aliphatichydrocarbon oils ordinarily used as transformer oils such as Wemco-Ctransformer oil, available from Westinghouse Electric Co., have alsobeen successfully utilized in the imaging process. Although these lessvolatile activators do not dry off by evaporation, image fixing can beaccomplished contacting the final image with an absorbent sheet such aspaper which absorbs the activator fluid. In short, any suitable volatileor non-volatile activator may be employed. Typical activators includeSohio Odorless Solvent 3440, an aliphatic (kerosene) hydrocarbonfraction, available from Standard Oil Co. of Ohio, carbon tetrachloride,petroleum ether, Freon 2114 (tetrafluorotetrachloropropane), otherhalogenated hydrocarbons such as chloroform, methylene chloride,trichloroethylene, perchloroethylene, chlorobenzene,trichloromonofluoromethane, trichlorotrifluoroethane,trichlorotrifluoroethane, ethers such as diethyl ether, diisopropylether, dioxane tetrahydrofuran, ethyleneglycol monoethyl ether, aromaticand aliphatic hydrocarbons such as benzene, toluene, xylene, hexane,cyclohexane, gasoline, mineral spirits and white mineral oil, vegetableoils such as coconut oil, babussu oil, palm oil, olive oil, castor oil,peanut oil and neatsfoot oil, decane, dodecane and mixtures thereof.Sohio Odorless Solvent 3440 is preferred because it is odorless,nontoxic and has a relatively high flash point.

Although the imaging layers may be prepared as selfsupporting films,normally these layers are coated onto a sheet referred to above as thedonor sheet or substrate. For convenience the combination of imaginglayer and donor sheet is referred to as the donor. When employing abinder, the electrically photosensitive material can be mixed in thebinder material by conventional means for blending solids as by ballmilling. After blending the ingredients of the imaging layer, the

desired amount is coated on a substrate. In a particularly preferredform of the invention an imaging layer comprising the electricallyphotosensitive material dispersed in a binder is coated onto atransparent, electrically insulating donor sheet.

The imaging layer may be supplied in any color desired either by takingadvantage of the natural color of the photosensitive material or bindermaterials in the imaging layer or by the use of additional dyes andpigments therein whether photoresponsive or not and, of course, variouscombinations of these photoresponsive and non-photoresponsive colorantsmay be used in the imaging layer so as to produce the desired color.

The donor sheet and receiver sheet may comprise any suitableelectrically insulating or electrically conducting material. Insulatingmaterials are preferred since they allow the use of high strengthpolymeric materials. Typical insulating materials include polyethylene,polypropylene, polyethylene, terephthalate, cellulose acetate, paper,plastic coated paper such as polyethylene coated paper, vinylchloride-vinylidene chloride copolymers and mixtures thereof. Mylar (apolyester formed by the condensation reaction between ethylene glycoland terephthalic acid available from E. I. duPont de Nemours & Co.,Inc.) is preferred because of its durability and excellent insulativeproperties. Not only does the use of this type of high strength polymerprovide a strong substrate for the positive and negative images formedon the donor substrate and receiver sheet but, in addition, it providesan electrical barrier between the electrodes and the imag ing layerwhich tends to inhibit electrical breakdown of the system whilesubjecting the manifold sandwich to an electrical field. The donor sheetand receiver sheet may each be selected from different materials. Thus amanifold sandwich can be prepared by employing an insulating donor sheetwhile a conductive material is employed as a receiver sheet.

A visible light source, an ultraviolet light source or any othersuitable source of electromagnetic radiation may be used to expose theimaging layer of this invention. The electrically photosensitivematerial is chosen so as to be responsive to the wavelength of theelectromagnetic radiation used. It is to be noted that differentelectrically photosensitive materials have different spectral responsesand that the spectral response of many electrically photosensitivematerials may be modified by dye sensitization so as to either increaseor narrow the spectral response of a material to a peak or to broaden itto make it more panchromatic in its response.

After subjecting the imaging layer to the electrification treatment ofthis invention, the imaging can be exposed to electromagnetic radiationeither prior to forming the manifold sandwich or after the formation ofthe manifold sandwich. Of course, if the imaging layer is exposed toelectromagnetic radiation after sandwich formation, the receiver sheetmust be transparent to such radiation. In most instances, by exposingthe imaging layer from the receiver side, the positive image is formedon the receiver sheet. That is, the illuminated portions of the imaginglayer adhere to the donor sheet and the non-illuminated areas of theimaging layer adhere to the receiver sheet. In addition, the activationstep can be included at any point in the manifold imaging process priorto the separation of the sandwich.

DESCRIPTION OF THE DRAWINGS The advantages of this improved method ofimaging will become apparent upon consideration of the detaileddisclosure of the invention especially when in conjunction with theaccompanying drawing wherein:

FIG. 1 is a side sectional view of a manifold sandwich.

FIG. 2 is a side sectional view diagramatically illustrating the processsteps of a preferred embodiment of the process of this invention.

Referring now to FIG. 1, there is shown donor sheet 11 upon which thereis resting an imaging layer generally indicated as 12 comprisingelectrically photosensitive particles 13 dispersed in an insulatingbinder 14. Over imaging layer 12 is laid a receiver sheet 16.

Referring now to FIG. 2, there is shown the optional activation step.Although the activator may be applied by any suitable techniques such aswith a brush, with a smooth or rough surfaced roller, by flow coating,by vapor condensation or the like, FIG. 2 shows the activator fluid 20being sprayed onto imaging layer 22 from container 24. Following thedeposition'of this activator fluid, imaging layer 22 supported by donorsheet 26 proceeds in the direction shown by the arrow into contact withreceiver sheet 28 which is supplied by roll 30. In certain instances theactivation step may be omitted. Thus, for example, a manifold sandwichmay be supplied wherein imaging layer 22 is initially fabricated to havea low cohesive strength so that activation may be omitted and receiversheet 16 may be placed on the surface of imaging layer 12 directly. Itis generally preferably, however, to include an activation step on theprocess because this allows the stronger imaging layers for purposes ofhandling prior to the actual imaging operation.

After receiver sheet 28 has been placed on imaging layer 22, anelectrical field is applied across the manifold sandwich throughelectrodes 32 and 34 which are connected to potential source 36 andresistor 38. Although FIG. 2 shows the manifold sandwich coming incontact with either electrode 32 or 34, they may contact one or bothelectrodes when the electrical field is applied depending upon the typeof electrode employed. Preferably the sandwich will contact at least oneelectrode to serve as a guide.

Alternatively, the charging electrode may be a corona discharge deviceor a friction charging device such as a furcovered roller. The sign ofthe charge as shown on electrodes 32 and 34 may also be reversed,electrode 32 being made negative and electrode 34 being made positive.In FIG. 2 both donor sheet 26 and receiver sheet 28 are electricallyinsulating thus retaining a static charge after being subjected to theelectric field by electrodes 32 and 34. After passing through electrodes32 and 34, the manifold sandwich proceeds in the direction of the arrow;and, as the sandwich passes between guide rollers 40, receiver sheet 28is rolled up on take-up roller 42 leaving the imaging layer 22 on donorsheet 26 since the electrical field is placed upon the manifold sandwichwhile in the darkllmaging layer 22 residing on donor sheet 26 proceedsin the direction of the arrow into contact with a second receiver sheet44 supplied from supply roll 46. The reformed manifold sandwich proceedsbetween electrodes 48 and 50 which are connected to a second potentialsource 52 through resistor 54. As before, electrodes 48 and 50preferably contact the manifold sandwich thus imparting an electricalcharge to the electrically insulating donor and receiver sheets and mayalternatively be a corona discharge device, a roller electrode or afriction charging device such as a furcovered roller. It is noted thatthe sign of the charge on electrodes 48 and 50 are reversed from thesign of the charge on electrodes 32 and 34 whereby the imaging materialis subjected to an electric field or reversed polarity prior to beingexposed to activating electromagnetic radiation.

After passing through electrodes 48 and 50 and retaining an electriccharge of the sign shown on the electrodes for the donor and receiversheet respectively, the manifold sandwich is exposed to activatingelectromagnetic radiation 56 which is in this case white incandescentlight. After image-wise exposure to the activating electromagneticradiation, the manifold sandwich then passes roller 58 which acts as aguide for the manifold sandwich and as a bearing point for the strippingapart of the receiver and donor sheets. Alternatively, roller 58 may bea sharp edge, a rod or a wire. Upon separation of donor sheet 26 andreceiver sheet 44, imaging layer 22 fractures along the edges of exposedareas and at the surface where it had adhered to donor sheet 26.Accordingly, once separation is complete, the exposed portions ofimaging layer 22 are retained on one of the sheets 26 and 28 while theunexposed portions are retained on the other sheet thus providing apositive image on one sheet and a negative image on the other sheet.

If a relatively volatile activator is employed, such as petroleum etheror carbontetrachloride, fixing of the image occurs almost instanteouslyafter separation of the sheets of 26 and 28 because the relatively smallquantity of activator in imaging layer 22 evaporates quickly. Withsomewhat less volatile activators, such as Sohio Odorless Solvent 3440or Freon 214 described above, fixing may be accelerated by blowing airover the images or warming them to about F. With the less volatileactivators, such as transformer oil, fixing is accomplished byabsorption of the activator into another layer such as paper. Many otherfixing techniques and methods for protecting the image such asovercoating, laminating with a transparent sheet and the like will occurto those skilled in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples furtherspecifically illustrate the present invention. The examples below areintended to illustrate various preferred embodiments of the improvedimaging method. The parts and percentages are by weight unless otherwiseindicated.

EXAMPLE I A commercial metal-free phthalocyanine is first purified byo-dichlorobenzene extraction to remove organic impurities. Since thisextraction step yields the less sensitive beta crystalline form, thedesired x form is obtained by dissolving about lOO grams of beta inapproximately 600 cc. of sulfuric acid precipitating it by pouring thesolution into about 3,000 cc. of ice water and washing with water toneutrality. The thus purified alpha phthalocyanine is then salt milledfor 6 days and desalted by slurrying in distilled water, vacuumfiltering, water washing and finally methanol washing until the initialfiltrate is clear. After vacuum drying to remove residual methanol, thex form phthalocyanine thus produced is used to prepare the imaging layeraccording to the following procedure: About grams of the x formphthalocyanine is added to about 5 grams of Algol Yellow GC,l,2,S,6-di(C,C-diphenyl) thiazoleanthraquinone, C. I. No. 67300,available from General Dyestuffs, and about 2.8 grams of purifiedWatchung Red B, l-(4'-methyl-5'-chloroazobenzene-2-sulfonicacid)-2-hydroxy-3-naphthoic acid, C. I. No. 15865, available from E. I.duPont de Nemours & Co., which is purified as follows: approximately 240grams of the Watchung Red B is slurried in about 2,400 milliliters ofSohio Odorless Solvent 3440, a mixture of kerosene fractions availablefrom the Standard Oil Company of Ohio. The slurry is then heated to atemperature of about 65C. and held there for about one-half hour. Theslurry is then filtered through a glass sintered filter. The solids arethen reslurried with petroleum ether (90 to 120C.) available fromMatheson, Coleman and Bell Division of the Matheson Company, EastRutherford, New Jersey and filtered through a glass sintered filter. Thesolids are then dried in an oven at about 50C.

About 8 grams of Sunoco Microcrystalline Wax Grade 5825 having anASTM-D-l27 melting point of 151F. and about 2 grams of Paraflint R. G.,a low molecular weight paraffinic material, available from the Moore &Monger Company, New York City and about 320 milliliters of petroleumether (90 to 120C.) and about 40 milliliters of Sohio Odorless Solvent3440 are placed with the pigments in a glass jar containing t z-inchflint pebbles. The mixture is then milled by revolving the glass jar atabout 70 r.p.m. for about 16 hours. The mixture is then heated forapproximately 2 hours at about 45C. and allowed to cool to roomtemperature. The mixture is then ready for coating on the donorsubstrate. The paste-like mixture is then coated in subdued green lightor 2-mil Mylar (a polyester formed by the condensation reaction betweenethylene glycol and tetrephthalic acid available from E. I. du- Pont deNemours & Co., Inc.) with a No. 36 wire wound drawdown rod to produce acoating thickness when dried of approximately 7% microns. The coatingand two mil Mylar sheet is then dried in the dark at a temperature ofabout 33C. for one-half hour. The coating is activated by applyingthereto Sohio Odorless Solvent 3440 by means of a soft brush and a 2-milthick Mylar receiver sheet is laid over the activated imaging layer.

The thus formed manifold sandwich is then placed receiver side down onthe tin oxide surface of a NESA glass electrode and a black conductivepaper electrode is laid over the donor side of the sandwich. Theelectrodes are connected to a 9,000 volt d.c. power supply in serieswith a 5,500 megohm resistor with the donor side electrode being madethe positive and the receiver side electrode being made the negativeelectrode. A

potential of about 9,000 volts is applied between the electrodes in thedark. With the potential applied, the donor sheet accompanied by theimaging layer is removed from the receiver sheet and the receiver sheeton the NESA glass is replaced by a fresh 2-mil Mylar receiver sheet. Theleads to the power supply from the electrodes are switched so as to makethe donor side electrode negative and the receiver side electrodepositive and the same voltage is again applied while in the dark. Withabout 9,000 volts applied a white incandescent light image is projectedupwards through the transparent glass electrode and the receiver sheetwith an illumination of approximately 0.1 foot-candles applied for 5seconds for a total incident energy of about 0.5 foot-candle seconds.The donor sheet together with the opaque electrode is peeled from themanifold sandwich thus fracturing the imaging layer in imagewiseconfiguration yielding a pair of excellent quality images with aduplicate of the original on the receiver sheet and a reversal ornegative image on the donor sheet.

EXAMPLE II The procedure of Example I is repeated except that afterimagewise exposure the polarity of the electric field is reversed againand the sandwich separated under the reversed field. A pair of excellentquality images are produced with a positive image residing on the donorsheet and a negative image on the receiver sheet.

Although specific components and proportions have been stated in theabove description of preferred embodiments of the invention, othertypical materials as listed above if suitable may be used with similarresults. In addition, other materials may be added to the mixture tosynergize, enhance or otherwise modify the properties of the imaginglayer. For example, various dyes, spectral sensitizer, or electricalsensitizers such as Lewis acids may be added to the several layers.

Other modifications and ramifications of the present invention willoccur to those skilled in the art upon a reading of the presentdisclosure. These are intended to be included within the scope of thisinvention.

What is claimed is:

l. An imaging process comprising the steps of:

a. providing an electrically photosensitive imaging layer sandwichedbetween a donor sheet and a transparent receiver sheet;

. subjecting said imaging layer to an electric field of known polarity.

. reversing the polarity of said electric field in the absence ofelectromagnetic radiation to which said imaging layer is sensitive;

. subsequent to reversal of the polarity of said electric field exposingsaid imaging layer to an imagewise pattern of electromagnetic radiationto which said layer is sensitive through said transparent receiver;

. separating said sandwich while under an electric field whereby saidimaging .layer fractures in imagewise configuration with the exposedportion of said imaging layer adhering to one of said donor and receiversheets and the unexposed portion adhering to the other sheet providedthat the imaging layer is structurally fracturable in response to thecombined effects of an applied electric field and exposure toelectromagnetic radiation to which it is sensitive upon the separationof the sandwich.

2. The process of claim 1 further including the step of modifying thepolarity of said electric field subsequent to imagewise exposure of theimaging layer wherein said modification involves reversing or reducingsaid field whereby the exposed and unexposed portions of said imaginglayer reverse adhesion.

3. The process of claim 1 further including the step of rendering saidlayer structurally fracturable in response to the combined effect of anapplied electric field and exposure to electromagnetic radiation byapplying thereto an activating amount of an activator for said layer.

4. The process of claim 1 wherein the electrically photosensitivematerial is an organic material.

5. The process of claim 4 wherein the electrically photosensitivematerial is phthalocyanine.

6. The method of claim 1 wherein the electrically photosensitivematerial is dispersed in an insulating .binder.

7. The method of claim 1 wherein the electric field is in the range offrom about 2,000 volts per mil to about 10,000 volts per mil.

8. The process of claim 2 wherein the electrically photosensitiveimaging material is dispersed in an insulating binder.

9. The process of claim 8 further including the step of rendering saidlayer structurally fracturable in response to the combined effect of anapplied electric field and exposure to electromagnetic radiation byapplying thereto an activating amount of an activator for said layer.

10. The process of claim 8 wherein the electrically photosensitivematerial is phthalocyanine.

11. The process of claim 1 wherein said donor and receiver sheets areelectrically insulating and said electric fields are provided byelectrostatic charges residing in said sheets.

12. The process of claim 1 further including the step of continuingexposure of said imaging layer after the exposed and unexposed portionsof said imaging layer adhere to one of said donor and receiver sheetsuntil the exposed and unexposed portions of the imaging layer reversesaid adhesion to said sheets.

2. The process of claim 1 further including the step of modifying thepolarity of said electric field subsequent to imagewise exposure of theimaging layer wherein said modification involves reversing or reducingsaid field whereby the exposed and unexposed portions of said imaginglayer reverse adhesion.
 3. The process of claim 1 further including thestep of rendering said layer structurally fracturable in response to thecombined effect of an applied electric field and exposure toelectromagnetic radiation by applying thereto an activating amount of anactivator for said layer.
 4. The process of claim 1 wherein theelectrically photosensitive material is an organic material.
 5. Theprocess of claim 4 wherein the electrically photosensitive material isphthalocyanine.
 6. The method of claim 1 wherein the electricallyphotosensitive material is dispersed in an insulating binder.
 7. Themethod of claim 1 wherein the electric field is in the range of fromabout 2,000 volts per mil to about 10,000 volts per mil.
 8. The processof claim 2 wherein the electrically photosensitive imaging material isdispersed in an insulating binder.
 9. The process of claim 8 furtherincluding the step of rendering said layer structurally fracturable inresponse to the combined effect of an applied electric field andexposure to electromagnetic radiation by applying thereto an activatingamount of an activator for said layer.
 10. The process of claim 8wherein the electrically photosensitive material is phthalocyanine. 11.The process of claim 1 wherein said donor and receiver sheets areelectrically insulating and said electric fields are provided byelectrostatic charges residing in said sheets.
 12. The process of claim1 further including the step of continuing exposure of said imaginglayer after the exposed and unexposed portions of said imaging layeradhere to one of said donor and receiver sheets until the exposed andunexposed poRtions of the imaging layer reverse said adhesion to saidsheets.